1. Field of the Invention
The invention concerns a method for filling casting molds with casting resin, or a similar casting-fluid liquid media, and the equipment with which to carry out the method.
2. Description of Related Art
When processing casting resins in pressure-molding, the casting resins are supplied either from pressurized vessels or by means of a multi-component metering and mixing apparatus to the particular casting molds.
When a pressurized vessel is used, the casting material, which is generally prepared under vacuum conditions, is transferred from a batch mixer into the pressurized vessel. Compressed air is used to move the casting material out of the pressurized vessel into the casting mold, as well as maintain the forming pressure.
As a rule, the pressurized vessel has adequate capacity for the number of molded articles which are cast sequentially at one time. Therefore, as the casting material ages during processing, correspondingly different viscosities result. To ensure constant quality when making the cast articles, constant filling rates of the subsequently manufactured cast articles are required. Because of the change in viscosity over time, the pressure must be constantly readjusted so that the rate of filling of the sequentially manufactured cast articles does not vary unduly.
Another drawback of pressurized vessels is that the previously vacuum-prepared casting material reacquires gases from the application of the compressed air.
European patent document 47 88 76 A1 describes a pressurized vessel in which the casting material is not directly exposed to compressed air. However, this design also has the disadvantage that quality differences arise among the cast articles on account of casting material aging. That is to say, when a substantial amount of time lapses between the initial and final casting from the same batch of casting material.
It is also known to use multi-component equipment such as that described in U.S. Pat. No. 4,307,760 to fill up casting molds with a continuous supply of casting material which does not contact air. However, the filling rate is kept constant only to the extent the viscosity of the material remains constant. This can be done only with difficulty, over an extended operating cycle.
The cast articles made by pressure-forming are most often used as insulators in electrical engineering and therefore the inclusion of even the tiniest air bubbles causes an unacceptable loss of quality and/or many articles to be rejected.